Dead or Alive 4 Unlockable: Nassau
The Nassau Station stage will become available when the SPARTAN-458 character is unlocked.

Dead or Alive 4 Unlockable: Tatami
Complete the story mode for all 17 characters. Unlock all hidden costumes for all 21 costumes. Unlock the system voice for all 22 characters. Note this stage is already available in Sparring mode -- this unlocks the stage for other modes.

Dead or Alive 4 Unlockable: Movie Theatre Mode
Beat story mode once.

Dead or Alive 4 Unlockable: System Voices
Complete a character's Exercise session in Sparring Mode. You can then go choose the voice heard during matches in the Settings menu.

Dead or Alive 4 Unlockable: Alpha-152's System Voice
Unlock the System voices for all 21 characters (Ein doesn't have one).

Dead or Alive 4 Unlockable: Tatami Stage
You must collect all of the costumes and finish all exercises in the game.

Dead or Alive 4 Unlockable: Hidden Commercial
Complete story mode with all of the characters.

Dead or Alive 4 Unlockable: Ayane Costume C3-C6
You must complete story mode with her once.

Dead or Alive 4 Unlockable: Hitomi C3-C8
Complete story mode.

Dead or Alive 4 Hint: Achievement Rank Shortcuts
Host a room with only three members in it. The person that is the host will receive the rank. The other two players join the fight, and when the fight starts, they should exit to their dashboards. When the game notices that both players have left the game the host will instantly rank up to SS, fight (and win) a single battle after you do this and you will unlock the SS achievement.

Submitted by dashboardfan1982

To downgrade all the way down to F-, follow the same steps as upgrading to SS, but instead of staying in the lobby when the players go to their dashboards, join the match as soon as they leave. You will see you points go down all the way until you are an F-. This is a great way to unlock all of the rank achievement, such as going from an SS to an S.

Submitted by Christopher Texidor

This way is easier and works better. First, get a party of three. Then have the de-ranker stay in the lobby. The two other players join the match and start. Pick the character you start on (Ayane or Kasumi) and once the game starts just fight each other. When the box appears in the corner of the screen, then the winner has to turn off his/her Xbox 360. Wait three seconds later and the other player turns off his/her Xbox 360. The de-rankers score should go down really fast. You can watch it go down on the players list. It will go all the way down to an F minus if you stay in the lobby. Play a game as a fminus to unlock that achievement.

Submitted by Corbintman007

Dead or Alive 4 Easter Egg
When you play as Spartan 158 at the casino, a Warthog may occasionally be part of the traffic instead of the normal cars.